Absorbent product



Sept. '13, 1960 A. A. BURGENI 2,952,260

ABSORBENT PRODUCT Filed April 23, 1958 s Sheets-Sheet 1 ATTC' RNEYvsvmwlmwvl Sept. 13, 1960 A. A. BURGENI 2,952,260

ABSORBENT PRODUCT 7 Filed April 23, 1958 3 Sheets-Sheet 3 INVENTORflzsezv A Baeaaw BY g hT RNEY ABSURBENT PRODUCT Alfred A. Burgeni, ShortHills, N J., assignor to Personal Products Corporation, a corporation ofNew Jersey Filed Apr. 23, 1958, Ser. No. 730,285 28 Claims. (Cl.128-290) This invention relates to an absorbent product and moreparticularly to an absorbent fibrous body containing short, absorbentcellulosic fibers which may be used as an absorbent component insanitary napkins and similar products for absorbing body fluids.

Short absorbent cellulosic fibers, such as comminuted Wood pulp fibersand cotton linters Whose lengths are in the region of about two mm. arelow in cost and readily available. They are particularly suitable foruse as absorbent components in numerous absorbent articles in the formof thick bats or plies because such bats have high bulk and volume, andrapidly absorb fluids. However, bats of such fibers are unstable, duemainly to the shortness of fiber length. They are tenuous and have lowcohesive and tensile strength, do not retain their shape and volume whencompressed or moistened, and have low capillary attraction and low fluidretentivity. When a bat of such fibers is saturated with fluid, it mats,becomes distorted and falls apart readily. When incorporated into anabsorbent article, such as a sanitary napkin, it has been commonpractice to include with such bats other components,.such as gauze,paper, or high bulk wadding, to impart to the napkin form and structuralstability and desired fluid flow and fluid absorbency characteristics. Asanitary napkin without these additional components lacked form andstructural stability and distorted readily in use upon the absorption offluid.

The fluid absorption and fluid flow characteristics of bats of wood pulpfibers and like short absorbent cellulosic fibers, while suitable insome respects are unsatisfactory in others. When fluid is applied to thesurface of a bat of such fibers, it penetrates the bat rapidly andstrikes through to the bottom surface. The fluid absorbed remainsessentially confined in the part of the bat directly under the area ofapplication; i.e. it is not distributed laterally through the bat to anyappreciable extent. Due to the low capillarity of the bat, it becomesquickly saturated with fluid in the region of application and its fullabsorbent capacity is not utilized. When a plurality of such bats isused, the bats still have poor fluid flow and fluid absorbencycharacteristics and, in elfect, act as a single bat.

Attempts to overcome the problems noted above have includedincorporating spacing elements and separate elements of paper and thelike having elongated compressed areas on their surfaces to formchanneling areas to aid in the distribution of fluid. However, inaddition to increasing the costs of manufacture of such napkins, theinclusion of such elements still required additional components toprovide form and structural stability and to obtain fluid penetrationand absorbency laterally of the napkin. The bats still possessed theirinherent disadvantages and their full potential had not been utilized.

'In accordance with this invention, absorbent products, such as sanitarynapkins, having as components thereof normally unstable fibrous batscontaining a major portion of short, absorbent cellulosic fibers, suchas comminuted wood pulp fibers, are provided with form and Sttes Patent'0 structural stability and improved fluid flow and fluid absorbencycharacteristics by incorporating therein a plurality of such bats whichhave been stabilized longitudinally and, in the preferred form of theinvention, transversely and longitudinally and which are so constructedand arranged as to provide for transmission of absorbed fluid from onebat to an adjacent bat. The absorbent products of the invention, ascontrasted to like products which do not have incorporated therein thenovel features of the invention, have increased capillarity, in-

, creased fluid retentivity and increased cohesive strength.

The invention contemplates a sanitary napkin consisting mainly of acover and an absorbent core containing short, absorbent cellulosicfibers in the form of a plurality of layers or plies provided with zonesof compacted and densified, cohered fibers to direct absorbed fluidlengthwise through the core and to impart longitudinal stability to thecore. Such a sanitary napkin may include a ply or plies with zones ofsimilar form and effect extending transversely of the plies, the zonesof the respective plies cooperating to absorb fluid and to transmit thefluid from one ply to an adjacent ply whereby the absorbingelfectiveness of the plies will be more fully utilized.

The invention also includes an absorbent core having zones of compactedand densified fibers and zones of uncompacted and undensified fibersarranged to define and limit the extent of absorption of fluid by thecore. The invention further includes an absorbent core having at leasttwo plies of short, absorbent, cellulosic fibers which plies have zonesof compacted and densified fibers having high cohesive strength,capillarity and fluid retentivity and zones of uncompacted andundensified relatively non-coherent fibers of relatively low capillarityand fluid retentivity, the zones of uncompacted and undensified fibersbeing contiguous, but preferably in face-toface contact, whereby fluidmay be transferred from one ply to-an adjacent ply through such zones.

The term contiguous zones includes zones which contact each other andalso zones which are near or adjacent each other and which may bebrought into operative relationship through the use of other componentswhich permit transmission of fluid in the desired manner.

Reference is made to the accompanying drawings and the followingdescription, wherein for illustrative purposes, the invention isdescribed in connection with a sanitary napkin. It is to be understood,however, that the invention is not to be so limited and may be utilizedin other products of similar function.

In the drawings,

Fig. 1 is a plan view of an integral web of absorbent fibers from whichan absorbent core of the invention may be formed, illustrating differentsections of the web provided with zones of compacted and densified,cohered fibers and zones of uncompacted and undensified, noncoheredfibers;

Fig. 2 is an enlarged sectional view of Fig. .1 along lines 22;

Fig. 3 is lines 3-3;

Fig. 4 is .an enlarged sectional view of Fig. .1 along lines 44;

Fig. 5 is a magnified view illustrating in more detail the fiber formand arrangement of compacted and densified fibrous zones and uncompactedand undensified zones through certain parts of the web;

Fig. 6 is a perspective view in the preferred form of web from which theabsorbent core of the invention may be formed, illustrating the build-upof certain areas thereon;

Fig. 7 is a perspective view of a sanitary napkin incoran enlargedsectional view of Fig. 1 along porating the absorbent core of theinvention, cut away to reveal its interior construction;

Fig. 8 is an enlarged section of the napkin of Fig. 7 along lines7-7,"and inverted;

. Fig. 9 is a view of Fig. Sill-ustrating the form the napkin of Fig. 7assumes when it is being worn in the preferred position; I

. Fig. 10 is an enlarged fragmentary view of the folded edge portion ofthe core formed by folding the webs of Figs. 1 and 6;

Fig. 11 is an enlarged view of a portion of the core illustrating thearrangement of the respective plies;

. Fig. 12 is a plan view of a variation of the left panel portion of theweb of Figs. 1 and 6;

. Fig. 13 is a vertical section of Fig. 12 along lines 10-'10.

Fig. 14 is still another variation of the left panel portion of the webof Figs. 1 and 6; and

Fig. '15 is a still further variation. 7

Referring to Fig. 1 of the drawings, there is shown a thickrectangular-shaped web or bat 10 of short absorbent, cellulosic fibrousmateria such as comminuted wood pulp fibers, cotton linters and thelike, from which an absorbent core embodying the invention may beformed. The absorbent core is formed by folding the web longitudinallyto form three superposed substantially co-extensive plies. By way ofexample, if it is desired to form an absorbent core 6.8 centimeters wideand 19.5 centimeters long for use in a sanitary napkin, the web would beabout three times as wide as the desired width of the core, i.e. about20 centimeters wide, and of the same length as the length of the core.Web 10 is divided into three parts or panels; a left panel 12, a centerpanel 14 and a right panel 16. The left panel includes the area of theweb from its left side edge to fold line xx; the center panel includesthe area of the web between fold lines xx and fold lines y-y; and theright panel includes the area of the web from fold line y-y to the rightside edge of the web.

The absorbent core is-formed from the web by first folding the leftpanel along fold lines xx over on top of the center panel and thenfolding the'right panel along lines y-y over the top of the folded leftpanel thereby forming three superposed plies with the left panelpositioned in the center. The resulting folded web provides a core whichhas the form illustrated in Fig. 7, inverted. The left' and centerpanels are approximately the same width and the right panel madeslightly wider to allow for the extra width needed to fold the rightpanel over both the left and center panels.

A simple folded conventional web of short, absorbent, cellulosic fibersof the type described above in connection with Fig. 1 is tenuous anddifficult to handle. Further an absorbent core formed from such a webpossesses essentially all the inherent disadvantages of the webincluding lack of form and structural stability, poor capillarity andlow tensile strength. In such form, its use in an absorbent product islimited and its use as the principal absorbent component in a sanitarynapkin would be unacceptable. 7

To provide the absorbent core with the necessary properties of strength,form and structural stability, dimensional stability, high capillarityand fluid absorbency, the center panel 14 of the web is provided with aseries of spaced longitudinally extending porous zones 18 in the form ofrectangular bands of compacted and densifi ed, cohered fibers. Thecompacted and densified zones may be continuous and extend the entirelength of the panel, as shown, although this is not essential.Preferably, the series of longitudinally extending densified zones offibers does not extend across the entirewidth of the panel, therebyleavingon each side zones 20 of relatively uncornpacted, uncompressedfibers.

Referring to Fig. 5, the longitudinally extending zones 18 of compactedand densified fibers preferably do not extend through the web thickness;however, they may do so. The fibers in these zones, because of theircompactness and density, have high capillarity and high fluidretentivity. The zones are sufliciently porous to permit fluid to beabsorbed readily and to spread longitudinally in the direction of thezones. The zones 22 between the zones 18 of compacted and densifiedfibers consist of relatively uncompacted, non-coherent fibers. The zones24 below the longitudinally extending zones may also be compacted anddensified and have relatively high capillarity and fluid retentivity.Preferably, however, zones 24 below are less densified and have lesscapillarity and fluid retentivity than zones 18. In the latter form,there is a transition in web characteristics through the web with regardto fiber density, coherency, capillarity and the like.

Again referring to Fig. 5, zones 18 in the web provide strength, formand structural stability to the web because of the compaction anddensification, and coherency of the fibers therein. They aresufliciently porous, while still integrated, to permit absorption andpenetration of fluid. The fibers in zones 22 and in zones 24 arerelatively less dense, uncompactedand more porous, but have lesscapillarity. There is thus provided in the center panel longitudinallyextending densified zones of compacted cohered fibers in part of thepanel and adjacent zones of relatively uncompacted, non-cohered fibers.

The longitudinally extending zones 18 of compacted and densified coheredfibers impart longitudinal form and structural stability to theabsorbent core and aid in integratingthe web structurally in thisdirection. In addition thereto, they impart desired fluid absorbency andfluid flow characteristics to the core. The zones possesshighcapillarity and high fluid retentivity withthe result that fluidimpinged thereon will be distributed longitudinally of the web along thezones. When these zones become saturated with fluid, the excess fluidwill spread to the adjacent relatively more porous zones 22, and in oneform of the invention to zones 24, of relatively uncompacted,undensified, non-cohered fibers. These parts of the Web act, in effect,as reservoirs for fluid.

Preferably, the side edge portions 20 of the center panel between theend longitudinally extending densified zones and the fold lines x-x andy--y are not formed with compacted and densified zones. In consequence,these parts of-the panel are relatively bulky and of high volume. Inthis form they have low capillarity, and fluid reaching thelongitudinally extending densified zones 18 will not tend to pass intothese side portions but instead will tend to be transmitted mainlylongitudinally in the direction of the longitudinally extendingdensified zones, thus minimizing side spread of fluid and maintainingthe side edges of the panel in a'relatively dry condition.

. As noted above, longitudinal strength, form and structural stabilityisimparted to the absorbent core by the longitudinally extending zones ofdensified cohered fibers. The core thus resists deformation in thelongitudinal direction. Transverse form and structural stability may beprovided by forming, by way of example, the left panel with transverselyextending spaced zones 26 of compacted and densified; cohered fiberslike those extending longitudinallyon the center panel. They arepreferably somewhat denser thanthe longitudinally extending zones in thecenter panel and desirably extend through the panel in these regions.Zones 26 have characteristics similar to those in the zones 18 extendinglongitudinally on the center panel with regard to compactedness,coherency, tensile strength, good shape and structural stability andhigh capillarity and fluid absorbency and retentivity. The zones 28 onthe left panel between the densified'zones 26 are similar to the zones22in the center panel as described in connection'with "Fig. 5. The fibersin these zones arerelatively uncompacted, undensified, non-coherent andof low capillarity. Preferably, the

transversely extending densified zones 26" on the left terminate shortthereof. This arrangement also minimizes the spread 'of absorbed fluidto theside edges of the panel. 1

In one suitable form of a sanitary napkin in accordance with theinvention, the transversely extending densified zones 26 on the leftpanel are in the form of elongated rectangles of appreciable lengthpositioned in the center of the panel. In addition thereto, similar, butconsiderably shorter, rectangular offset zones 30 are alternatelypositioned in the spaces between the centrally positioned densifiedzones and at the ends thereof. Zones 30, which have the physicalcharacteristics of transversely extending zones 26, act as a furtherbarrier to the flow of fluid to the'side edges of the panel.

The right panel 16 does not have densified zones and has essentiallythecharacteristics of the Web as it is formed from the comminuted Wood pulpfibers. Its principal purpose is to provide the desired thickness andbulk to the absorbent core to aid in integrating the-structure and toabsorb any fluid which may penetrate the center panel.

A suitable absorbent core embodying the invention for use in a sanitarynapkin may be made from the web of Fig. 1 by comminuting sheet Wood pulpin a mill to individualize the fibers, laying the fibers in the form ofa thick bat 20 centimeters wide to a bulk density of about 0.031 gramper cc. and weighing 0.032 gram per square centimeter, and then sprayingthe surfaces of the web parts described above, specifically, the leftand center panels, with about 0.003 ccs. of water per square centimeterof web surface. The amount of moisture applied to the surface of the Webmay be varied, but it is suflicient to insure the formation of coherentbonds. such as hydrate bonds, between the cellulosic fibers in the zonesdesired upon the application of pressure.

Preferably, the left panel is formed with transversely extending zonesof densified, cohered fibers which extend.

substantially through the entire thicknessof the left panel, therebyimparting somewhat greater transverse strength to the left panel. As aconsequence, the bottom surface of the left panel may have transverselyextending corrugations 32 almost as distinctly defined as those formedon the top portion of the panel. This may be obtained by applyinggreater amounts of pressure to the left panel. The amounts of moistureand pressure may be suitably varied over a wide range as is known toprovide transversely extending zones which have the desired propertiesin varying degrees, of porosity, high tensile strength, coherency, highcapillarity, and the like.

Directly after the web is moistened, it is passed beneath compressingrollers having a peripheral form suitable to provide the densified zonesof the desired shape on the left and center panels and compressed withsulficient pressure to form the coherent compacted and densified zones.

The center panel, which is approximately 6.8 centimeters Wide, may beprovided with eight, nine, or even more longitudinally extendingdensifiedzones 18 centrally positioned in the center panel, and beingabout 2 millimeters wide and spaced about 2.7 millimeters apart, therebyextending over a Width of about 40 millimeters. The left panel havingabout the same width as the center panel, is provided with centrallypositioned transversely extending densified zones 26 39 millimeterslong, 3.5 millimeters wide and spaced 3.5 millimeters.

The combination of moisture and pressure on the selected portions of theweb results in the formation of the porous zones of compacted anddensified, cohered fibers. The remaining portions of the web notcontacted by the moisture and not compressed by the compression rollersremains relatively uncompacted, undensified .and non-coherent. In thecenter panel some embossing 34 may be obtained on the surface of thepanel opposite that to which moisture and compression is applied, and inthe interior of the web, due to the compressing-eifect exerted upontheseparts of the web by the compressing roller. -Inthe left panel, it isthat the zones of densified fibers extend through the panel. The web maythen be folded along the fold lines of Fig. 1 to form the absorbent corein the manner described above, and enclosed within a cover or wrapper ofsuitable form.

The amount of moisture which may be applied to the web may vary, as forexample, from about 0.002 to about 0.02 ccs. per square centimeter ofweb surface. When greater amounts of moisture are applied to the surfaceof the 'Web, the moisture will penetrate deeper into the interior of theweb. Consequently, when the moistened web is subjected to compression,somewhat denser zones of compacted cohered fibers will form. The amountof compression applied may also be suitably varied over a range as, forexample, from about 10 to about 50 pounds per square inch. The amountsof moisture and compression applied are controlled on the basis of webthickness and density to provide porous, densified, coherent fibrouszones of high capillarity while simultaneously leaving the adjacentfibrous areas relatively uncompacted and non-coherent. Suflicientamounts of moisture and pressure are applied so that adjacent fibers inthe moistened, compressed zones will be coherent, thereby integratingthe fibers in the zones, and the absorbent core.

In Fig. 6, there is illustrated a web 36 of fibers from preferred, asnoted above,

which an absorbent core embodying a preferred aspect of the invention ismade. The web is basically similar to that illustrated in Fig. l and hasa left panel 12a, center panel 14a and right panel 16a. In additionthereto, the center panel 14a and the right panel 16a are provided withincreased thickness on their center portions by adding plies 38 and 40,respectively, of absorbent fibrous material, to increase the bulk andvolume of the absorbent core. The built up areas on the center and rightpanels may be formed integrally with the remainder of the Web at thesame time, or alternatively, may be formed as separate webs and thenplaced upon the panels.

A suitable web incorporating the features illustrated in Fig. 6 may beformed by first providing a base Web by comminuting sheet wood pulp andlaying the individualized fibers as a bat having the desireddimensionssuch as that described above in connection with Fig. 1 andweighing 0.020 gram per square cm. and having a bulk density of 0.031gram per cubic centimeter. The additional ply 38 of absorbent fibersabout 42 millimeters wide and of the same length as the length of theweb is placed centrally upon the center panel 14a of the web. The plymay be of any suitable Weight and bulk density and preferably weighsabout 0.028 gram per square cm. The second ply 40 is placed centrally onthe right panel 16a. This ply may also have substantially the Weight andsize of that placed on the center panel; preferably, it weighs about0.020 gram per square centimeter. The left and center panels of the webare then sprayed with moisture. Preferably, the left panel is sprayedwith .less moisture than the right panel. By way of example, the leftpanel may be sprayed with 0.0012 ccs. of water per square centimeter ofsurface area and the center panel with 0.0045 ccs. of water per squarecentimeter of surface area. After the web panels have been sprayed withmoisture, the web is then compressed by passing through compressingrollers having peripheral surfaces of suitable form to provide thelongitudinally extending densified zones 18a and undensified zones 22aon the center panel, and the transversely extending densified zones 26aand undensified zones 28a, and the shorter, rectangular offset zones30a, on the left panel.

In Fig. 11 there is illustrated the manner in which the superposed pliesformed by folding the webs of Fig. 1 and Fig. 6 cooperate with eachother to enable fluid absorbed by one ply to be transmitted to anadjacent ply. As illustrated in Fig. 11, and referring to Fig. 6, thelongitudinally extending densified zones 18a on the 7 centerpanel'ar'edepressed below the top surface o'f'th'e paneLfQ'Ihetransverselyextending densified zones 26a and the'oifset zones 30a on the leftpanel' are similarly depressed. The zones, 22a and 28a on the respectivepanels between the depressed densified zones are relatively uncompactedand undensified.

When the plies are superposed, the zones of undensified fibers intersectand contact each other at their points of intersection. Due to theiruncompacted, undensified structure the zones are highly porous to fluid.Accordingly, when the center panel 14a, or a region thereof,becomessaturated with fluid, the excess fluid will be transferred fromthe center panel to the left panel 12a throughthe uncompressed,undensified zones 22a on the center panel to the contiguous uncompressedzones 28a on theleft panel. Transferrence of excess fluid from thecenter panel to the left panel through these zones is rapid and henceover-saturation of the center panel is minimized. As the excess fluidenters the left panel through its zones of uncompacted and undensifiedfibers, it is drawn into the transversely extending densified zones 26aand the offset zones 30a whereupon, because of the high capillarity ofthese zones, the fluid is spread transversely of the left panel. In thismanner, the absorbing effectiveness of the left panel is utilized.

The contiguous zones of uncompacted, undensified fibers .on the left andcenter panels may be arranged in any suitable manner whereby fluid willbe transferred from the center to the left panel. If desired, a web offluid permeable material, such as a thin, porous web of absorbentfibers, may be interposed between the left and center panels. 'In thisform of the invention one side of the web would contact the uncompressedzones 28a on the left panel and the other side the uncompressed. zones22a on the center panel, thereby providing for transmission of fluidfrom the zones of uncompacted fibers on one panel through the Web to thezones of uncompacted fibers on the other panel. Other suitablearrangements involving the inclusion of separate or additional elementsbetween the panels may be employedv while still retaining the desiredfluid transmission features of the invention.

A sanitary napkin 42 incorporating the absorbent core of the inventionand illustrated in Figs. 7-9 exemplifies the manner in which thearrangement of the compacted and densified, cohered fiber zones and theuncompacted and undensified, non-coherent zones in the various pliescooperate to provide the necessary form and structural stability to thesanitary napkinwhile also providing the desired fluid flow and fluidabsorbency characteristics. The absorbent core portion of the napkinmaybe formed by folding the Web of Fig. l or Fig. 6 in the manner describedabove. Referring to Fig. 6, after folding, the ends of the folded webmay be cut, if desired, along the dotted lines 44 in an arcuate shape toform rounded ends on the absorbent core; The absorbent core so formed isenclosed within an outer cover or wrapper 46 of any suitable material,such as a permeable woven or non-woven fabric, having ends48 extendingbeyond the ends of the absorbent core for attaching the napkin inposition on the body of the wearer. V

Preferably, the napkin incorporating the absorbent core formed from thefolded Web of Fig. 6 is placed in position on the body in a positioninverted from that illustrated in Fig. 7 and in the manner illustratedin Figs. 8 and 9 so that the surface 50 of the center panel opposite theside having the longitudinally extending densified zones is placedagainst the body. 7 In this manner ofplacement a surface area ofrelatively soft, highly porous, loosely compacted fibers will beadjacent the body and provide comfort. However, the napkin may be wornin a reversed position. V

7 When fluid contacts surface 50' of the napkin, it rapidly penetratesthe center panel into the interior of the absor bent core due to theuncompacted, highly porous nature 8 of the' surface fibers. Only a smallstain pattern is formed on the surface of the napkin and lateraldistribution of the fluid over the surface of the napkin is minimized.;As the fluid penetrates through the loosely uncompacted surface fibers,it contacts the inner portion of the center panel having thelongitudinally extending zones 18a of densified fibers of highcapil'larity whereupon the fluid is directed along the length of theabsorbent core in the direction oflthe longitudinally extendingdensified zones. When the longitudinally extending densified zonesbecome saturated with fluid, the fluid spreads into the ad-. jacentzones 22a of relatively uncompacted fibers between the densified zones18a. These zones are relatively uncompacted and have low capillarity andbecause of their high bulk and volume can store large amounts of fluid.If a zone of densified fibers adjacent the zone of undensified fibers isdry and has not been moistened with fluid,

the fluid will be drawn by the dry zone of densified fibers:

from the moistened zone of undensified fibers because the densified zonehas higher capillarity and then will be distributed longitudinally alongthe densified zone. By this arrangement, the absorbency features of thecenter panel are effectively utilized.

When the centerpanel or a region thereof becomes saturated with fluid,excess fluid is transferred to the left panel 12a, which is positioneddirectly below, primarily through the contiguous zones 22a and 28a ofuncompacted and undensified fibers whereupon it is transferredtransversely in densified zones in the left panel in a manner similar tothat in which fluid is transmitted longitudinally in the center panel.Further, as the transversely extending densified zones in the centerpanel become saturated with fluid, the intervening zones of uncompacted,undensified fibers receive the excess fluid and retain it. .It is thusseen that fluid passing from the center panel to the left panel isdistributed laterally in the left panel after passing through the centerpanel, to' utilize the absorbent effectiveness of the panel. Preferably,to prevent fluid absorbed by the panel from reaching the side edges ofthe panel and contacting the body of the wearer, the transverselyextending densified zones terminate short of the side edges of thepanel. The areas between the ends of the transversely extendingdensified zones and the side edges of the left panel consist ofrelatively uncompacted, undensified fibers having low capillarity andhigh volume. Accordingly, when fluid reaches the ends of thetransversely extending densified zones, it will be restricted fromspreading to these areas.

Transverse and longitudinal form and structural stability and thedesired fluid flow characteristics may be imparted to the absorbent coreof the invention through the use of zones of compacted and densifiedfibers and zones of uncompacted, undensified fibers of various forms. InFig. 12, compacted and densified zones in the form of spaced, slightlyarcuate bands 52 are shown positioned in the center of the panel andterminate short of the side edges thereof' In this form, there is alsoprovided a spaced pair of longitudinally extending densified zones 54 oneach side of the ends of the arcuate, transversely extending densifiedzones. Zones 54 are spaced slightly from arcuate zones 52 to minimizespreading of fluid passing beyond the ends of the arcuate zones and totransfer it longitudinally in the direction of the length of the panel,thereby preventing the fluid from striking through to the sides of thepanel.

In Fig. '14, the transversely extending, densified zones 56 are in theform of flat Us and in Fig. 15 the zones 58 are sinuous.

The variations illustrated in Figs. 14 and l5.do not discloselongitudinally extending densified zones of the type shown in Fig. 12,but may include 'such zones or other suitablemodifications. Thelongitudinally, extending zoneson the center panel may also be similarlyvaried in form. I i

- T The zones of uncompacted and undensified fibers be-' Q tween thedensified zones 'ineach-of the left panels of the foregoing examples areshaped similarly to the 'densified zones and are contiguous in :partwith the longitudinally extending zones of like characteristics on thecenter panel.

By Way of example, there has been illustrated and described an absorbentcore of the invention formed by folding an integral web having therespective panel portions including the longitudinally and transverselyextending uncompacted'and u'ndens'ified zones as in Figs. 1 and 6. Theformation of the absorbent core from an integral folded web hasadvantages and in some respects is pre ferred; however, the inventioncontemplates absorbent cores made from superposed individual plies ofabsorbent material. With an integral folded web shifting of the plies isminimized and further core stability is obtained. This feature isillustrated in Fig. wherein there is shown a fold edge of the coreformed by folding the plies on top of each other. The fibers 60 in theweb at the fold 62 integrate the absorbent core and hold together therespective superposed plies by forming a sidewall 64 common to theplies.

his to be understood that web forms other than those referred to abovemay be used, that the absorbent core of the invention may be formed fromfolded or unfolded webs having 'densified zones of differentconfigurations and arranged in diflerent laminar relationships, and thatothernumerous variations andmodifications may be made withtout'departingfrom the spirit-of the invention.

It is also to be understood that although the invention is particularlyadapted to the making of highly absorbent cores from short, absorbentcellulosic fibers such as comminuted wood pulp fibers and cottonlinters, the invention is not limited to cores of these short fibers,but is applicable to the making of similar cores from other similarfibers of different lengths.

This invention is a continuation-impart of my cop'ending applications,Ser. No. 579,083, filed April 18, 1956',

and Ser. No. 587,015, filed May 24, 1956.

What isclaimed is:

1. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having longitudinally extendingporous zones of compacted and densified, coherent fibers having highcapillarity and fluid retentivity and intervening zones of looselyassociated relativelyuncompacted fibers having high volume, lowcapillarity and fluid retentivity, another of said r-plies having porouszones "of compacted and densified, coherent fibers and intervening zonesof loosely associated uncompacted fibers extending transversely of saidply, at least parts of said zones of uncompacted fibers in said pliesbeing contiguous, whereby fluid may be transferred from oneply to theother ply.

2. Foruse in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing comminutedwood pulp fibers, one of said plies having longitudinally extendingporous zones of compacted and densified, coherent fibers having highcapillarity and fluid retentivity and intervening zones of looselyassociated relatively uncompacted'fibers having high volume, lowcapillarity and fluid retentivity, another of --said plies having porouszones of compacted and densified, coherent fibers and intervening zonesof loosely associated uncompacted fibers extending transversely of saidply, at least parts' of said zones of uncompacted fibers in said pliesbeing contiguous, whereby fluid may be transferred from one ply to anadjacent ply.

3. For use in-an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies formed from a folded webcontaining absorbent, cellulosic fibers, one of said plies havinglongitudinally extending porous zones of compacted and densified,coheren't'fibers having high capillarity and fluid retentivity andintervening zones of loosely associated relatively uncompacted fibershaving'high volume, low capillarity and fluid retentivity, another ofsaid plies having porous zones of compacted and densified, coherentfibers and intervening zones of loosely associated uncompacted fibersextending transversely of said ply, at least parts of said zones ofuncompacted fibers in said plies being contiguous whereby fluid may betransferred from one ply to the other ply.

4. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbent,cellulosic fibers, one of said plies having longitudinally extendingporous zones of compacted and densified, coherent fibers having highcapillarity and fluid retentivity and intervening zones of looselyassociated relatively uncompacted fibers having high volume, lowcapillarity and fluid retentivity, another of said plies having porouszones of compacted and densified, coherent fibers and intervening zonesof loosely associated uncompacted fibers extending transversely of saidply, said zones of uncompacted fibers in said plies intersecting eachother and being contiguous at the intersections whereby fluid may betransferred from one ply to the other ply.

5. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having longitudinally extendingdepressed porous zones of compacted and densified, coherent fibershaving high capillarity and fluid retentivity and intervening raisedzones of loosely associated relatively uncompacted fibers having highvolume, low capillarity and fluid reten tivit-y, another of said plieshaving depressed porous zones of compacted and densified, coherentfibers and intervening raised zones of loosely associated uncompactedfibers extending transversely-of said ply, at least parts of said raisedzones of uncompacted fibers in said plies being contiguous whereby fluidmay be transferred from one ply to the adjacent ply.

6. For use in an absorbent product, an absorbent-core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having longitudinally extendingporous zones of compacted and densified, coherent fibers having highcapillarity and fluid retentivity'and intervening zones of looselyassociated relatively uncompacted fibers having high volume, lowcapillarity and fluid retentivity, an adjacent ply having porous zonesof compacted and densified, coherent fibers and intervening zones ofloosely associated uncompacted fibers extending transversely of saidply, the compacted and densified, transversely extendingzones on saidadjacent ply terminating short of the side edges thereof, at least partsof said zones of uncompacted fibers in said plies being contiguous,whereby fluid may be transferred from one .ply to anadjacent ply.

7. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having continuous, longitudinallyextending porous zones of. compacted and densified, coherent,hydratebonded cellulosic fibers having high capillarity and fluidretentivity and intervening zones of loosely associated relativelyuncompacted fibers having high volume, low capillarity and fluidretentivity, an adjacent ,ply having porous zones of compacted anddensified, coherent, hydrate-bonded cellulosic fibers and interveningzones of loosely associated uncompacted fibers extending transversely ofsaid ply, the compacted and densified, transversely extending zoneson'said adjacent ply terminating short of the side edges thereof, atleast parts of said zones of uncompacted fibers insaid plies beingcontiguous, whereby fluid maybe transferred from one ply to'the adjacentply.

8. A sanitary napkin having an absorbent core and a cover for said core,said core comprising a plurality of superposed absorbent fibrous pliescontaining absorbent cellulosic fibers, :one of said plies havinglongitudinally extending porous zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity andintervening zones of loosely associated relatively uncompacted fibershaving high volume, low capillarity and fluid retentivity, another plyhaving porous zones of compacted and densified, coherent fibers andintervening zones of loosely associated uncompacted fibers extendingtransversely of said ply, at least parts of said zones of uncompactedfibers in said plies being contiguous whereby fluid may be transferredfrom one ply to the other ply.

9. A sanitary napkin having an absorbent core and a cover for said core,said core comprising a plurality of superposed absorbent fibrous pliescontaining absorbent cellulosic fibers, an outer ply havinglongitudinally extending porous zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity andintervening zones of loosely associated relatively uncompacted fibershaving high volume, low capillarity and fluid retentivity, an adjacentinner ply having porous zones of compacted and densified, coherentfibers and intervening zones of loosely associated uncompacted fibersextending transversely of said ply, at least part of said zones ofuncompacted fibers in said plies being contiguous, whereby fluid may betransferred from the outer ply to the adjacent inner ply.

10. A sanitary napkin having an absorbent core and a cover for saidcore, said core comprising a plurality of superposed absorbent fibrousplies formed from a folded web containing absorbent cellulosic fibers,an outer ply having continuous longitudinally extending porous zones ofcompacted and densified, coherent fibers having high capillarity andfluid retentivity and intervening zones of loosely associated relativelyuncompacted fibers having high volume, low capillarity and fluidretentivity, an adjacent inner ply having porous zones of compacted anddensified, coherent fibers and intervening zones of loosely associateduncompacted fibers extending transversely of said ply, at least part ofsaid zones of uncompacted fibers in said plies being contiguous, wherebyfluid may be transferred from the outer ply to the adjacent inner ply.

11. A sanitary napkin having an absorbent core and a cover for saidcore, said core comprising a plurality of superposed absorbent fibrousplies containing comminuted wood pulp fibers, an outer ply havingcontinuous longitudinally exending porous zones of compacted anddensified, hydrate-bonded cellulosic fibers having high capillarity andfluid retentivity and intervening zones of loosely associated relativelyuncompacted fibers having high volume, low capillarity and fluidretentivity; an adjacent inner ply having porous zones of compacted anddensified, hydrate-bonded cellulosic fibers and intervening zones ofloosely associated uncompacted fibers extending transversely of saidply, the compacted and densified transversely extending zones on saidadjacent inner ply terminating short of the side edges thereof, saidzones of uncompacted fibers in said plies intersecting each other andbeing contiguous at the intersections, whereby fluid may be transferredfrom the outer ply to the adjacent inner ply.

12. A sanitary napkin having an absorbent core and a cover for saidcore, said core comprising a plurality of superposed absorbent fibrousplies containing absorbent cellulosic fibers, an outer ply havinglongitudinally extending depressed porous zones of compacted anddensified, coherent fibers having high capillarity and fluid retentivityand intervening raised zones of loosely associated relativelyuncompacted fibers having high volume, low capillarity and fluidretentivity, an adjacent inner ply having depressed porous zones ofcompacted and densi-- fied,v coherent fibers and intervening raisedzones of loosely associated uncompacted fibers extending transversely ofsaid ply, at least part of said zones of uncompacted fibers in saidplies being contiguous, whereby fluid may be transferred from the outerplyto the adjacent innerply;

13(A sanitary napkin having an absorbent core and a cover for said core,said core comprising a plurality of superposed absorbent fibrous pliesformed from a single web containing'comminuted wood pulp fibers, anouter ply having longitudinally extending depressed porous zones ofcompacted and densified, hydratebonded cellulosic fibers having highcapillarity and fluid retentivity and intervening raised zones ofloosely associated relatively uncompacted fibers having high volume, lowcapillarity and fluid retentivity, an adjacent inner ply havingdepressed porous zones of compacted and densified, hydrate-bondedcellulosic fibers and inter vening raised zones of loosely associateduncompacted fibers extending transversely of said ply, the compacted anddensified transversely extending 'zones on said adjacent inner plyterminating short of the side edges thereof, at least part of said zonesof uncompacted fibers in said plies being contiguous, whereby fluid maybe transferred from the outer ply to the adjacent inner ply,

14. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having a plurality oflongitudinally extending porous zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity andsimilarly extending zones of loosely associated relatively uncompactedfibers having high volume and low capi1- larity and fluid retentivity,another of said plies also having zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity extendingtransversely of said ply, said compacted and densified fibrous zonesimparting form and structural stability to said core.

15. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having a plurality of spaced,longitudinally extending porous zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity andintervening zones of loosely associated relatively uncompacted fibershaving high volume and low capillarity and fluid retentivity, another ofsaid plies also having zones of compacted and densified, coherent fibershaving high capillarity and fluid retentivity and intervening zones ofloosely associated relatively uncompacted fibers extending transverselyof said ply, said compacted and densified fibrous'zones imparting formand structural stability to said core. p

16. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having a plurality of spaced,longitudinally extending porous zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity andintervening zones of loosely associated relatively uncompacted fibershaving high volume and low capillarity and fluid retentivity, another ofsaid plies also having zones of compacted and densified, coherent fibershaving high capillarity and fluid retentivity and intervening 'zones ofloosely associated relatively uncompacted fibers extending transverselyof said ply, said transversely extending compacted and densified zonesterminating short of the side edges of said ply, said ply also havingzones of compacted and densified, coherent fibers offset from saidtransversely extending zones and at the ends thereof, said compacted anddensified fibrous zones imparting form and structural stability to saidcore. V

17. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of' said plies having a plurality of spaced,longitudinally extending porous zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity versely ofsaid ply and terminating short of and intervening zones of looselyassociated relatively uncompacted fibers-having high' volume and lowcapillarity and fluid retentivity, "another of said plies also havingzones of compacted and densified, coherent fibers having highcapillarity and fluid retentivity and intervening zones of looselyassociated relatively uncompacted fibers extending transversely of saidply, said transversely extending compacted and densified zonesterminating short of the side edges of said ply, said ply also havinglongitudinally extending porous zones of compacted and densified,coherent fibers between, the ends of said transversely extending zonesof compacted and densified, coherent fibers and the side edges of saidply, said compacted and densified fibrous zones imparting form andstructural stability to said core.

18. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having a'plurali-ty oflongitudinally extending porous zones of compacted and densified,coherent hydratebonded cellulosic fibers having high capillarity andfluid retentivity and intervening zones of loosely associated relativelyuncompacted fibers having high volume and low capillarity and fluidretentivity, another of said plies also having zones of compacted anddensified, coherent hydrate-bonded cellulosic fibers having highcapillarity and fluid retentivity extending transversely of said ply,said compacted and densified fibrous zones imparting form and structuralstability to said core.

19. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having a plurality oflongitudinally extending porous zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity andsimilarly extending zones of loosely associated relatively uncompactedfibers having high volume and low capillarity and fluid retentivity,another of said plies also having zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity extendingtransversely of and through said ply, said compacted and densifiedfibrous zones imparting formand structural stability to said core.

20. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having a plurality oflongitudinally extending porous zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity andsimilarly extending zones of loosely associated relatively uncompactedfibers having high volume and low capillarity and fluid retentivity,another of said plies also having zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity extendingtransthe side edges of said ply, said compacted and densified fibrouszones imparting form and structural stability to said core.

21. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies containing absorbentcellulosic fibers, one of said plies having a plurality of spaced,longitudinally extending porous zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity andsimilarly extending zones of loosely associated relatively uncompactedfibers having high volume and low capillarity and fluid retentivity,another of said plies also having zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity extendingtransversely of said ply, said compacted and densified fibrous zonesterminating short of the side edges of said plies, the fibers in theplies between the compacted and densified zones and the side edges orthe plies being relatively loosely associated and uncompacted, saidcompacted and densified fibrous zones imparting form and structuralstability to said core.

22. For use in an absorbent product, an absorbent core comprising aplurality of superposed absorbent fibrous plies formed ,from an integralfolded web, said plies containing absorbent cellulosic fibers, one ofsaid plies having a plurality of spaced, elongated longitudinallyextending porous zones of compacted and densified, coherent fibershaving high capillarity and fluid retentivity and similarly extendingzones of loosely associated rel-ativ'ely uncompacted fibers having highvolume and low capillarity and fluid retentivity, another of said pliesalso having zones of compacted and densified, coherent fibers havinghigh capillarity and fluid retentivity extending transversely of saidply, said compacted and densified fibrous zones imparting form andstructural stability to said core.

23. For use in an absorbent product, an absorbent core comprising a,plurality of superposed absorbent fibrous plies of comminuted WOOd pulpfibers, one of said plieshaving a plurality of longitudinally extendingporous zones of compacted and densified, coherent fibers having highcapillarity and fluid retentivity and similarly extending zones ofloosely associated relatively uncompacted fibers having high volume andlow capillarity and fluid retentivity, another of said plies also havingzones of compacted and densified, coherent fibers having highcapillarity and fluid retentivity extending transversely of said ply,said compacted and densified fibrous zones imparting form and structuralstability to said core.

24. A sanitary napkin having an absorbent core and a cover for saidcore, said core comprising a plurality of superposed absorbent fibrousplies containing absorbent cellulosic fibers, an outer ply having aplurality of longitudinally extending porous zones of compacted anddensified, coherent fibers having high capillarity and fluid retentivityand similarly extending zones of loosely associated relativelyuncompacted fibers having high volume and low capillarity and fluidretentivity, an inner ply also having zones of compacted and densified,coherent fibers having high capillarity and fluid retentivity extendingtransversely of said ply, said compacted and densified fibrous zonesimparting form and structural stability to said napkin.

25. A sanitary napkin having an absorbent core and a cover for saidcore, said core comprising a plurality of superposed absorbent fibrousplies containing absorbent cellulosic fibers, an outer ply having on itsinner side a plurality of longitudinally extending porous zones ofcompacted and densified, coherent fibers having high capillarity andfluid retentivity and similarly extending zones of loosely associatedrelatively uncompacted fibers having high volume and low capillarity andfluid retentivity, an inner ply also having zones of compacted anddensified, coherent fibers having high capillarity and fluid retentivityextending transversely of said ply, said compacted and densified fibrouszones imparting form and structural stability to said napkin.

26. A sanitary napkin having an absorbent core and a cover for saidcore, said core comprising a plurality of superposed absorbent fibrousplies containing absorbent cellulosic fibers, an outer ply having on itsinner side a plurality of longitudinally extending porous zones ofcompacted and densified, coherent fibers having high capillarity andfluid retentivity and similarly extending zones of loosely associatedrelatively uncompacted fibers having high volume and low capillarity andfluid retentivity, an inner adjacent ply also having zones of compactedand densified, coherent fibers having high capillarity and fluidretentivity extending transversely of said ply, said transverselyextending zones terminating short of the side edges of said ply, saidcompacted and densified fibrous zones imparting form and structuralstability to said napkin.

27. A sanitary napkin having an absorbent core and a cover for saidcore, said core comprising a plurality of superposed absorbent fibrousplies containing comminuted wood pulp fibers, an outer ply havingonitsinner side a plurality of longitudinally extending porous zones ofcompacted and densified, coherent fibers having high capillarity andfluid retentivity and similarly extending zones of loosely associatedrelatively uncompacted fibers having high volume and low capillarity andfluid retentivity, an adjacent side on an adjacent inner ply also havingZones of compacted and densified, coherent fibers having highcapillarity and fluid retentivity extending transversely of said ply,said compacted and densified fibrous Zones imparting form and structuralstability to said napkin.

28. A sanitary napkin having an absorbent core and a cover for saidcore, said core comprising a plurality of superposed absorbent fibrousplies containing comminuted Wood pulp fibers, an outer ply having on itsinner side a plurality of spaced, continuous, longitudinally extendingporous zones of compacted and densified, coherent fibers having highcapillarity and fluid retentivity and intervening zones of looselyassociated relatively uncompacted fibers having high volume and lowcapillarity and fluid retentivity, an adjacent side on an 4 inner plyalso having zones of compacted and densified;

coherent fibers having high capillarity and fluid retentivity andintervening zones of loosely associatedtuncompacted fibers extendingtransversely of said ply, said transversely extending compacted anddensified' zones terminating short of the side edges of the ply, saidply also having zones of compacted and densified, coherent fibers ofisetfrom said transversely extending zones and at the ends thereof, saidcompacted and densified fibrous zones imparting form and structuralstability to said napkin.

References Cited in the file of this patent UNITED STATES PATENTS1,863,333 Heitmeyer June 14, 1932 2,073,410 Thomas Mar. 9, 19372,508,214 Biedennan May 16, 1950 2,618,816 Joa Nov. 25, 1952 2,826,200Brien et al Mar. 11, 1958 FOREIGN PATENTS 428,344 Great Britain May 10,1935

